ANSI/IEEE Standards regulate the accepted dimensions, for example, length and depth, for all VME type electronic circuit cards utilized with standard communications backplanes. VME type circuit cards are generally provided in lengths that depend on the number of attached connectors for interfacing with the backplane. For example, a circuit card of length 3 U has one backplane connector. Cards of lengths 6 U and 9 U have two and three backplane connectors, respectively. Circuit cards are also provided in a number of standard depths. Two of the most popular depths are 160 mm and 220 mm, but other depths, both shorter and taller, are commercially available.
VME cards are typically installed in system chassis enclosures by inserting the edges of the cards in opposed card guides mounted to the enclosure walls. Mounted to each card guide are a number of guide slots corresponding to slot locations for the backplane that accept and retain the card edges. Installation of each circuit card is completed by inserting the attached card connector into a mating connector on the backplane. Through the connector and backplane, each installed VME circuit card may communicate with other installed VME cards and the electronic system.
Historically, prior art card guides mounted within system chassis enclosures have only been able to accommodate one depth per slot location. Furthermore, the system chassis was designed to segregate slot locations for circuit cards of different lengths into different designated areas of the chassis enclosure through the use of fixed partitions. These partitions were also used, where necessary, to separate slot locations for circuit cards of different depths. Thus, circuit card slot locations within the enclosure were inflexibly dedicated at the time the system chassis and circuit board configuration was first designed.
The disadvantage of the prior art system chassis design and card guide mounting system is that the number of slots chosen for a given dimension circuit card in a designated partitioned area is fixed for the life of the chassis. Furthermore, the slot location chosen for a particular dimension and function circuit card is also fixed. In this manner, the chassis enclosure for the electronic system is limited in available expansion area and unable to adapt to replacement or modified circuit designs implemented on circuit cards having dimensions different than the original design. The inability to adapt to or accommodate redesigned circuit cards of other standard dimensions regardless of slot location severely limits the life span of the enclosure. This often necessitates complete enclosure replacement at considerable cost to accommodate subsequent updated or redesigned versions of the electronic system.
Accordingly, there is a need for an adaptable mounting system for electronic circuit card enclosures capable of accepting for installation cards of varying standard dimensions regardless of slot location. With such a system, modifications or redesigns of individual circuit cards may be implemented without additionally requiring the chassis enclosure to be redesigned.